Method by a user equipment, method by a base station, user equipment, and base station

ABSTRACT

A method by a User Equipment (UE) is described. The method includes receiving, from a radio access network, one or more radio resource control (RRC) messages. The one or more RRC messages are used to configure a dual connectivity in which the UE communicates with the radio access network using a first set of cell(s) and a second set of cell(s) and to configure a signaling radio bearer (SRB) for the second set of cell(s). The one or more RRC messages are sent via a signaling radio bearer of the first set of cell(s).

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/825,862 entitled “DEVICES FOR ESTABLISHING MULTIPLE CONNECTIONS,”filed Aug. 13, 2015, which is a continuation of U.S. patent applicationSer. No. 13/744,403 entitled “DEVICES FOR ESTABLISHING MULTIPLECONNECTIONS,” filed Jan. 17, 2013, and now issued as U.S. Pat. No.9,144,091, which are all hereby incorporated by reference in theirentirety.

TECHNICAL FIELD

The present disclosure relates generally to communication systems. Morespecifically, the present disclosure relates to devices for establishingmultiple connections.

BACKGROUND

Wireless communication devices have become smaller and more powerful inorder to meet consumer needs and to improve portability and convenience.Consumers have become dependent upon wireless communication devices andhave come to expect reliable service, expanded areas of coverage andincreased functionality. A wireless communication system may providecommunication for a number of wireless communication devices, each ofwhich may be serviced by a base station. A base station may be a devicethat communicates with wireless communication devices.

As wireless communication devices have advanced, improvements incommunication capacity, speed, flexibility and efficiency have beensought. However, improving communication capacity, speed, flexibilityand efficiency may present certain problems.

For example, wireless communication devices may communicate with one ormore devices using a communication structure. However, the communicationstructure used may only offer limited flexibility and efficiency. Asillustrated by this discussion, systems and methods that improvecommunication flexibility and efficiency may be beneficial.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating one configuration of one or moreevolved Node Bs (eNBs) and one or more user equipments (UEs) in whichsystems and methods for establishing multiple connections may beimplemented;

FIG. 2 is a flow diagram illustrating one implementation of a method forestablishing multiple connections by a UE;

FIG. 3 is a flow diagram illustrating one implementation of a method forestablishing multiple connections by a first eNB;

FIG. 4 is a block diagram illustrating configurations of EvolvedUniversal Terrestrial Radio Access Network (E-UTRAN) architecture inwhich systems and methods for establishing multiple connections may beimplemented;

FIG. 5 is a block diagram illustrating another configuration of E-UTRANarchitecture for multi-connectivity in which systems and methods forestablishing multiple connections may be implemented;

FIG. 6 is a block diagram illustrating a carrier aggregationconfiguration in which a first cell and a second cell are co-located,overlaid and have equal coverage;

FIG. 7 is a block diagram illustrating a carrier aggregationconfiguration in which a first cell and a second cell are co-located andoverlaid, but the second cell has smaller coverage;

FIG. 8 is a block diagram illustrating a carrier aggregationconfiguration in which a first cell and a second cell are co-located butthe second cell antennas are directed to the cell boundaries of thefirst cell;

FIG. 9 is a block diagram illustrating a carrier aggregationconfiguration in which a first cell provides macro coverage and remoteradio heads (RRH) on a second cell are used to improve throughput athotspots;

FIG. 10 is a block diagram illustrating a carrier aggregationconfiguration in which frequency selective repeaters are deployed;

FIG. 11 is a block diagram illustrating multiple coverage scenarios forsmall cells with and without macro coverage;

FIG. 12 is a block diagram illustrating one configuration of a userplane protocol stack for multi-connectivity;

FIG. 13 is a block diagram illustrating another configuration of a userplane protocol stack for multi-connectivity;

FIG. 14 is a block diagram illustrating a configuration of a controlplane protocol stack for a single radio resource control (RRC)connection;

FIG. 15 is a block diagram illustrating a configuration of a controlplane protocol stack with multiple RRC connections;

FIG. 16 is a block diagram illustrating one configuration of RRC messagemanagement;

FIG. 17 is a block diagram illustrating a configuration of a controlplane protocol stack with multiple control plane terminations;

FIG. 18 illustrates various components that may be utilized in a UE;

FIG. 19 illustrates various components that may be utilized in an eNB;

FIG. 20 is a block diagram illustrating one configuration of a UE inwhich systems and methods for sending feedback information may beimplemented; and

FIG. 21 is a block diagram illustrating one configuration of an eNB inwhich systems and methods for receiving feedback information may beimplemented.

DETAILED DESCRIPTION

A method by a UE is described. The method includes establishing a firstradio interface between the UE and a first point on an E-UTRAN. Themethod also includes establishing a second radio interface between theUE and a second point on the E-UTRAN by using the first radio interface.The method further includes mapping data radio bearers (DRBs) to atleast one of the first radio interface and the second radio interface.

All DRBs may be mapped to one radio interface. A first DRB set may bemapped to the first radio interface and a second DRB set may be mappedto the second radio interface.

One or more RRC messages sent or received by the UE may terminate at oneof the first point or the second point. At least one RRC message sent orreceived by the UE may terminate at the first point and at least one RRCmessage may terminate at the second point.

The first point may be connected to a mobility management entity (MME)and the second point may be connected to one or more of a servinggateway (S-GW) and a proxy gateway between the second point and theS-GW. The first point may be a termination for a user plane protocol andthe second point may be a termination for a control plane protocol.

The first point may be connected to a MME and to an S-GW. The firstpoint may be a termination for a user plane protocol and may be atermination for a control plane protocol.

A method by a first eNB is also described. The method includesconnecting to a UE with a first radio interface. The method alsoincludes connecting to a second eNB. The UE is connected to the secondeNB with a second radio interface. The method further includes mappingDRBs to at least one of the first radio interface and the second radiointerface.

A UE is also described. The UE includes a processor and memory inelectronic communication with the processor. The UE also includesinstructions stored in the memory. The instructions are executable toestablish a first radio interface between the UE and a first point on anE-UTRAN. The instructions are also executable to establish a secondradio interface between the UE and a second point on the E-UTRAN byusing the first radio interface. The instructions are further executableto map DRBs to at least one of the first radio interface and the secondradio interface.

An eNB is also described. The eNB includes a processor and memory inelectronic communication with the processor. The eNB also includesinstructions stored in the memory. The instructions are executable toconnect to a UE with a first radio interface. The instructions are alsoexecutable to connect to a second eNB. The UE is connected to the secondeNB with a second radio interface. The instructions are furtherexecutable to map DRBs to at least one of the first radio interface andthe second radio interface.

The 3rd Generation Partnership Project, also referred to as “3GPP,” is acollaboration agreement that aims to define globally applicabletechnical specifications and technical reports for third and fourthgeneration wireless communication systems. The 3GPP may definespecifications for next generation mobile networks, systems and devices.

3GPP Long Term Evolution (LTE) is the name given to a project to improvethe Universal Mobile Telecommunications System (UMTS) mobile phone ordevice standard to cope with future requirements. In one aspect, UMTShas been modified to provide support and specification for the EvolvedUniversal Terrestrial Radio Access (E-UTRA) and Evolved UniversalTerrestrial Radio Access Network (E-UTRAN).

At least some aspects of the systems and methods disclosed herein may bedescribed in relation to the 3GPP LTE, LTE-Advanced (LTE-A) and otherstandards (e.g., 3GPP Releases 8, 9, 10, 11 and/or 12). However, thescope of the present disclosure should not be limited in this regard. Atleast some aspects of the systems and methods disclosed herein may beutilized in other types of wireless communication systems.

A wireless communication device may be an electronic device used tocommunicate voice and/or data to a base station, which in turn maycommunicate with a network of devices (e.g., public switched telephonenetwork (PSTN), the Internet, etc.). In describing systems and methodsherein, a wireless communication device may alternatively be referred toas a mobile station, a UE, an access terminal, a subscriber station, amobile terminal, a remote station, a user terminal, a terminal, asubscriber unit, a mobile device, etc. Examples of wirelesscommunication devices include cellular phones, smart phones, personaldigital assistants (PDAs), laptop computers, netbooks, e-readers,wireless modems, etc. In 3GPP specifications, a wireless communicationdevice is typically referred to as a UE. However, as the scope of thepresent disclosure should not be limited to the 3GPP standards, theterms “UE” and “wireless communication device” may be usedinterchangeably herein to mean the more general term “wirelesscommunication device.”

In 3GPP specifications, a base station is typically referred to as aNode B, an eNB, a home enhanced or evolved Node B (HeNB) or some othersimilar terminology. As the scope of the disclosure should not belimited to 3GPP standards, the terms “base station,” “Node B,” “eNB,”and “HeNB” may be used interchangeably herein to mean the more generalterm “base station.” Furthermore, one example of a “base station” is anaccess point. An access point may be an electronic device that providesaccess to a network (e.g., Local Area Network (LAN), the Internet, etc.)for wireless communication devices. The term “communication device” maybe used to denote both a wireless communication device and/or a basestation.

It should be noted that as used herein, a “cell” may be anycommunication channel that is specified by standardization or regulatorybodies to be used for International Mobile Telecommunications-Advanced(IMT-Advanced) and all of it or a subset of it may be adopted by 3GPP aslicensed bands (e.g., frequency bands) to be used for communicationbetween an eNB and a UE. “Configured cells” are those cells of which theUE is aware and is allowed by an eNB to transmit or receive information.“Configured cell(s)” may be serving cell(s). The UE may receive systeminformation and perform the required measurements on all configuredcells. “Activated cells” are those configured cells on which the UE istransmitting and receiving. That is, activated cells are those cells forwhich the UE monitors the physical downlink control channel (PDCCH) andin the case of a downlink transmission, those cells for which the UEdecodes a physical downlink shared channel (PDSCH). “Deactivated cells”are those configured cells that the UE is not monitoring thetransmission PDCCH. It should be noted that a “cell” may be described interms of differing dimensions. For example, a “cell” may have temporal,spatial (e.g., geographical) and frequency characteristics.

The systems and methods disclosed herein describe devices forestablishing multiple connections. This may be done in the context of anevolved universal terrestrial radio access network (E-UTRAN). Forexample, establishing multiple connections between a user equipment (UE)and two or more eNBs on an E-UTRAN is described. In one configuration,the two or more eNBs may have different schedulers.

The systems and methods described herein may enhance carrieraggregation. Carrier aggregation refers to the concurrent utilization ofmore than one component carrier (CC). In carrier aggregation, more thanone cell may be aggregated to a UE. In one example, carrier aggregationmay be used to increase the effective bandwidth available to a UE. Intraditional carrier aggregation, a single eNB is assumed to providemultiple serving cells for a UE. Even in scenarios where two or morecells may be aggregated (e.g., a macro cell aggregated with remote radiohead (RRH) cells) the cells may be controlled (e.g., scheduled) by asingle eNB. However, in a small cell deployment scenario, each node(e.g., eNB, RRH, etc.) may have its own independent scheduler. Tomaximize the efficiency of radio resources utilization of both nodes, aUE may connect to two or more nodes that have different schedulers.

In one configuration, for a UE to connect to two nodes (e.g., eNBs) thathave different schedulers, multi-connectivity between the UE and E-UTRANmay be utilized. For example, in addition to Rel-11 operation, a UEoperating according to the Rel-12 standard may be configured withmulti-connectivity (which may also be referred to as dual connectivity,inter-eNB carrier aggregation, multi-flow, multi-cell cluster, multi-Uu,etc.). The UE may connect to the E-UTRAN with multiple Uu interfaces, ifconfigured. For instance, the UE may be configured to establish one ormore additional radio interfaces by using one radio interface.Hereafter, one node is called as primary eNB (PeNB) and another node iscalled as secondary eNB (SeNB).

Various examples of the systems and methods disclosed herein are nowdescribed with reference to the Figures, where like reference numbersmay indicate functionally similar elements. The systems and methods asgenerally described and illustrated in the Figures herein could bearranged and designed in a wide variety of different implementations.Thus, the following more detailed description of severalimplementations, as represented in the Figures, is not intended to limitscope, as claimed, but is merely representative of the systems andmethods.

FIG. 1 is a block diagram illustrating one configuration of one or moreevolved Node Bs (eNBs) 160 and one or more user equipments (UEs) 102 inwhich systems and methods for establishing multiple connections may beimplemented. The one or more UEs 102 may communicate with one or moreeNBs 160 using one or more antennas 122 a-n. For example, a UE 102transmits electromagnetic signals to the eNB 160 and receiveselectromagnetic signals from the eNB 160 using the one or more antennas122 a-n. The eNB 160 communicates with the UE 102 using one or moreantennas 180 a-n. It should be noted that one or more of the UEsdescribed herein may be implemented in a signal device in someconfigurations. For example, multiple UEs may be combined into a singledevice in some implementations. Additionally or alternatively, one ormore of the eNBs described herein may be implemented in a single devicein some configurations. For example, multiple eNBs may be combined intoa single device in some implementations. In the context of FIG. 1, forinstance, a single device may include one or more UEs 102 in accordancewith the systems and methods described herein. Additionally oralternatively, one or more eNBs 160 in accordance with the systems andmethods described herein may be implemented as a single device ormultiple devices.

The UE 102 and the eNB 160 may use one or more channels 119, 121 tocommunicate with each other. For example, a UE 102 may transmitinformation or data to the eNB 160 using one or more uplink channels121. Examples of uplink channels 121 include a physical uplink controlchannel (PUCCH) and a physical uplink shared channel (PUSCH), etc. Theone or more eNBs 160 may also transmit information or data to the one ormore UEs 102 using one or more downlink channels 119, for instance.Examples of downlink channels 119 include a PDCCH, a PDSCH, etc. Otherkinds of channels may be used.

Each of the one or more UEs 102 may include one or more transceivers118, one or more demodulators 114, one or more decoders 108, one or moreencoders 150, one or more modulators 154, a data buffer 104 and a UEoperations module 124. For example, one or more reception and/ortransmission paths may be implemented in the UE 102. For convenience,only a single transceiver 118, decoder 108, demodulator 114, encoder 150and modulator 154 are illustrated in the UE 102, though multipleparallel elements (e.g., transceivers 118, decoders 108, demodulators114, encoders 150 and modulators 154) may be implemented.

The transceiver 118 may include one or more receivers 120 and one ormore transmitters 158. The one or more receivers 120 may receive signalsfrom the eNB 160 using one or more antennas 122 a-n. For example, thereceiver 120 may receive and downconvert signals to produce one or morereceived signals 116. The one or more received signals 116 may beprovided to a demodulator 114. The one or more transmitters 158 maytransmit signals to the eNB 160 using one or more antennas 122 a-n. Forexample, the one or more transmitters 158 may upconvert and transmit oneor more modulated signals 156.

The demodulator 114 may demodulate the one or more received signals 116to produce one or more demodulated signals 112. The one or moredemodulated signals 112 may be provided to the decoder 108. The UE 102may use the decoder 108 to decode signals. The decoder 108 may produceone or more decoded signals 106, 110. For example, a first UE-decodedsignal 106 may comprise received payload data, which may be stored in adata buffer 104. A second UE-decoded signal 110 may comprise overheaddata and/or control data. For example, the second UE-decoded signal 110may provide data that may be used by the UE operations module 124 toperform one or more operations.

As used herein, the term “module” may mean that a particular element orcomponent may be implemented in hardware, software or a combination ofhardware and software. However, it should be noted that any elementdenoted as a “module” herein may alternatively be implemented inhardware. For example, the eNB operations module 182 may be implementedin hardware, software or a combination of both.

In general, the UE operations module 124 may enable the UE 102 tocommunicate with the one or more eNBs 160. The UE operations module 124may include one or more of a UE radio interface determination module128, a UE data radio bearer (DRB) mapping module 130 and a UE radioresource control (RRC) message determination module 132.

The UE radio interface determination module 128 may establish a firstradio interface between the UE 102 and a first point on an EvolvedUniversal Terrestrial Radio Access Network (E-UTRAN). For example, thefirst point may include a first eNB 160 belonging to an E-UTRAN. In oneconfiguration, the first eNB 160 may be referred to as a primary eNB(PeNB). The UE radio interface determination module 128 may connect tothe first point (e.g., eNB 160) with a Uu interface. The Uu interfacemay also be referred to as a primary Uu interface. The Uu interface maybe a radio interface between the UE 102 and the first eNB 160.

The UE 102 may be configured to establish a second radio interfacebetween the UE 102 and a second point on the E-UTRAN (e.g., second eNB160) by using the first radio interface. In one configuration, the UE102 may be configured by the first eNB 160 to connect to the E-UTRANwith multiple radio interfaces. Therefore, upon connecting with thefirst eNB 160, the eNB 160 may configure the UE 102 to establishadditional radio interfaces using the first radio interface. The UEradio interface determination module 128 may connect to the second eNB160 using the second radio interface. The second eNB 160 may be referredto as a secondary eNB (SeNB). In one configuration, the PeNB and theSeNB have different schedulers. The UE radio interface determinationmodule 128 may connect to the second eNB 160 with a Uux interface. TheUux interface may also be referred to as a secondary Uu interface.

The UE 102 may not be required to be aware of the PeNB and SeNB as longas the UE 102 is aware of the multiple Uu interfaces with the E-UTRAN.In one configuration, the UE 102 may see an eNB 160 as a point on theE-UTRAN. In another configuration, the UE 102 may see the multiple Uuinterfaces with the E-UTRAN as connections with multiple points on theE-UTRAN. In yet another configuration, the E-UTRAN may provide multipleUu interfaces with the same or different eNBs 160. For instance, thePeNB and SeNB could be the same eNB 160. The multiple Uu interfaces(e.g., multi-connectivity) may be achieved even by a single eNB 160. Inother words, in one configuration, the systems and methods describedherein may be achieved by a single eNB 160 or a single scheduler. The UE102 may be able to connect more than one Uux interface (e.g., Uu1, Uu2,Uu3, etc.). Each Uu interface may be used to perform carrier aggregation(CA). Therefore, the UE 102 may be configured with more than one set ofserving cells in a CA scenario.

It should be noted that while multiple Uu interfaces are described, thesystems and methods described herein may be realized by a single Uuinterface or a single radio interface depending on the definition ofinterface. For example, a radio interface may be defined as an interfacebetween the UE 102 and the E-UTRAN. In this definition, the interface isnot an interface between the UE 102 and an eNB 160. For example, oneradio interface can be defined as an interface between UE 102 and theE-UTRAN with multi-connectivity. Therefore, the Uu interface and Uuxinterface discussed above may be considered as different characteristicsof cells. For instance, the Uu interface may be a first set of cell(s)and the Uux interface may be a second set of cell(s). Also, the firstradio interface may be rephrased as a first set of cell(s) and thesecond radio interface may be rephrased as a second set of cell(s).

The UE DRB mapping module 130 may map DRBs to at least one of the firstradio interface and the second radio interface. A DRB (Data RadioBearer) is a radio bearer that carries user data (as opposed to controlplane signaling). For example, a DRB may be mapped to the user planeprotocol stack. The user plane protocol stack may include packet dataconvergence protocol (PDCP), radio link control (RLC), medium accesscontrol (MAC) and physical (PHY) layers. For instance, when a DRB isestablished by RRC signaling from the eNB 160 to the UE 102, a PDCPentity, an RLC entity (or entities), and a Dedicated Traffic Channel(DTCH) logical channel may be established. For each DRB, a PDCP entity,an RLC entity (or entities), and a DTCH logical channel are established.For one radio interface, DRBs may use a MAC entity and a PHY entity. DRBconfigurations (e.g., DRB addition, modification and release) mayinclude PDCP configuration, RLC configuration and/or logical channelconfiguration.

In one configuration, all DRBs (e.g., DRB1, DRB2, DRB3 . . . ) may bemapped to one radio interface. For example, the user plane may use onlythe Uux interface. Therefore, all DRBs may be mapped to the Uuxinterface. In another configuration, the DRBs may be organized into DRBsets that may be mapped to different radio interfaces. For example, afirst DRB set (e.g., DRB1, DRB2, DRB3 . . . ) may be mapped to the firstradio interface (e.g., the Uu interface) and a second DRB set (e.g.,DRB4, DRB5, DRB6 . . . ) may be mapped to the second radio interface(e.g., the Uux interface). The DRB mapping is discussed in more detailin FIG. 12 and FIG. 13.

The UE RRC message determination module 132 may send or receive one ormore RRC messages. The RRC protocol may convey control plane signaling,through which the E-UTRAN may control the behavior of the UE 102. Formulti-connectivity operation (e.g., multiple Uu interface operation),the UE 102 may have one RRC connection, may have multiple RRCconnections or may have one RRC connection and multiple sub-RRCconnections. In one configuration, the one or more RRC messages sent bythe UE RRC message determination module 132 may terminate at a singlepoint on the E-UTRAN. For example, the UE RRC message determinationmodule 132 may send RRC messages toward (or receive RRC messages from) asingle point on the E-UTRAN. Therefore, the one or more RRC messages mayterminate at one of the first eNB 160 or the second eNB 160.

In another configuration, the one or more RRC messages may terminate atmultiple points on the E-UTRAN. For example, the UE 102 may send RRCmessages toward (or receive RRC messages from) multiple addressed pointson the E-UTRAN. Therefore, at least one RRC message may terminate at thefirst eNB 160 and at least one RRC message may terminate at the secondeNB 160. Multiple scenarios for conveying RRC messages are discussed inmore detail in FIG. 14 through FIG. 17.

The UE operations module 124 may provide information 148 to the one ormore receivers 120. For example, the UE operations module 124 may informthe receiver(s) 120 when or when not to receive transmissions based onthe uplink grant.

The UE operations module 124 may provide information 138 to thedemodulator 114. For example, the UE operations module 124 may informthe demodulator 114 of a modulation pattern anticipated fortransmissions from the eNB 160.

The UE operations module 124 may provide information 136 to the decoder108. For example, the UE operations module 124 may inform the decoder108 of an anticipated encoding for transmissions from the eNB 160.

The UE operations module 124 may provide information 142 to the encoder150. The information 142 may include data to be encoded and/orinstructions for encoding. For example, the UE operations module 124 mayinstruct the encoder 150 to encode transmission data 146 and/or otherinformation 142. The other information 142 may include the DRBs and theRRC messages.

The encoder 150 may encode transmission data 146 and/or otherinformation 142 provided by the UE operations module 124. For example,encoding the data 146 and/or other information 142 may involve errordetection and/or correction coding, mapping data to space, time and/orfrequency resources for transmission, multiplexing, etc. The encoder 150may provide encoded data 152 to the modulator 154.

The UE operations module 124 may provide information 144 to themodulator 154. For example, the UE operations module 124 may inform themodulator 154 of a modulation type (e.g., constellation mapping) to beused for transmissions to the eNB 160. The modulator 154 may modulatethe encoded data 152 to provide one or more modulated signals 156 to theone or more transmitters 158.

The UE operations module 124 may provide information 140 to the one ormore transmitters 158. This information 140 may include instructions forthe one or more transmitters 158. For example, the UE operations module124 may instruct the one or more transmitters 158 when to transmit asignal to the eNB 160. The one or more transmitters 158 may upconvertand transmit the modulated signal(s) 156 to one or more eNBs 160.

The eNB 160 may include one or more transceivers 176, one or moredemodulators 172, one or more decoders 166, one or more encoders 109,one or more modulators 113, a data buffer 162 and an eNB operationsmodule 182. For example, one or more reception and/or transmission pathsmay be implemented in an eNB 160. For convenience, only a singletransceiver 176, decoder 166, demodulator 172, encoder 109 and modulator113 are illustrated in the eNB 160, though multiple parallel elements(e.g., transceivers 176, decoders 166, demodulators 172, encoders 109and modulators 113) may be implemented.

The transceiver 176 may include one or more receivers 178 and one ormore transmitters 117. The one or more receivers 178 may receive signalsfrom the UE 102 using one or more antennas 180 a-n. For example, thereceiver 178 may receive and downconvert signals to produce one or morereceived signals 174. The one or more received signals 174 may beprovided to a demodulator 172. The one or more transmitters 117 maytransmit signals to the UE 102 using one or more antennas 180 a-n. Forexample, the one or more transmitters 117 may upconvert and transmit oneor more modulated signals 115.

The demodulator 172 may demodulate the one or more received signals 174to produce one or more demodulated signals 170. The one or moredemodulated signals 170 may be provided to the decoder 166. The eNB 160may use the decoder 166 to decode signals. The decoder 166 may produceone or more decoded signals 164, 168. For example, a first eNB-decodedsignal 164 may comprise received payload data, which may be stored in adata buffer 162. A second eNB-decoded signal 168 may comprise overheaddata and/or control data. For example, the second eNB-decoded signal 168may provide data (e.g., PUSCH transmission data) that may be used by theeNB operations module 182 to perform one or more operations.

In general, the eNB operations module 182 may enable the eNB 160 tocommunicate with the one or more UEs 102. The eNB operations module 182may include one or more of an eNB interface determination module 194, aneNB DRB mapping module 196 and an eNB RRC message determination module198.

The eNB interface determination module 194 may connect to a UE 102 witha first radio interface. For example, a first eNB 160 may belong to anE-UTRAN. In one configuration, the first eNB 160 may be referred to as aprimary eNB (PeNB). The eNB interface determination module 194 mayconnect to the UE 102 with a Uu interface as described above.

The eNB interface determination module 194 may determine whether the UE102 may be configured to connect to a second eNB 160 with a second radiointerface. In one configuration, the eNB interface determination module194 may configure the UE 102 to connect to the E-UTRAN with multipleradio interfaces. Therefore, upon connecting with the UE 102 (using thefirst radio interface), the eNB interface determination module 194 mayconfigure the UE 102 to establish additional radio interfaces.

The eNB interface determination module 194 may connect to a second eNB160. For example, upon being configured for multi-connectivity (usingthe first radio interface), the UE 102 may connect to the second eNB 160with a second radio interface (e.g., Uux interface). The second eNB 160may be referred to as a secondary eNB (SeNB). The eNB interfacedetermination module 194 may connect to the second eNB 160 to facilitatemulti-connectivity and carrier aggregation. The eNB interfacedetermination module 194 may connect to the second eNB 160 using one ormore X interfaces. The first eNB 160 and the second eNB 160 may exchangedata (e.g., DRBs and RRC messages) across the one or more X interfaces.In one configuration, the first eNB 160 and the second eNB 160 havedifferent schedulers.

The eNB DRB mapping module 196 may map DRBs to at least one of the firstradio interface and the second radio interface. In one configuration,all DRBs may be mapped to one radio interface. For example, the userplane may use only the Uux interface. Therefore, all DRBs may be mappedto the Uux interface. In another configuration, the DRBs may beorganized into DRB sets that may be mapped to different radiointerfaces. For example, a first DRB set may be mapped to the firstradio interface (e.g., the Uu interface) and a second DRB set may bemapped to the second radio interface (e.g., the Uux interface). The DRBmapping is discussed in more detail in FIG. 12 and FIG. 13.

The eNB RRC message determination module 198 may send or receive one ormore RRC messages. The RRC protocol may convey control plane signaling,through which the E-UTRAN may control the behavior of the UE 102. Formulti-connectivity operation (e.g., multiple Uu interface operation),the UE 102 may have one RRC connection, may have multiple RRCconnections or may have one RRC connection and multiple sub-RRCconnections. In one configuration, the one or more RRC messages sent orreceived by the eNB RRC message determination module 198 may terminateat a single point on the E-UTRAN. For example, the eNB RRC messagedetermination module 198 may receive all RRC messages sent by the UE102. Therefore, each of the one or more RRC messages may terminate atthe first eNB 160.

In another configuration, the one or more RRC messages may terminate atmultiple points on the E-UTRAN. For example, the UE 102 may send RRCmessages toward multiple addressed points on the E-UTRAN. The eNB RRCmessage determination module 198 may determine whether an RRC messageterminates at the first eNB 160 or at the second eNB 160 based on theaddress included with an RRC message. Therefore, at least one RRCmessage may terminate at the first eNB 160 and at least one RRC messagemay terminate at the second eNB 160. Multiple scenarios for conveyingRRC messages are discussed in more detail in FIG. 14 through FIG. 17.

The eNB operations module 182 may provide information 190 to the one ormore receivers 178. For example, the eNB operations module 182 mayinform the receiver(s) 178 when or when not to receive transmissionsbased on the DRBs and the RRC messages.

The eNB operations module 182 may provide information 188 to thedemodulator 172. For example, the eNB operations module 182 may informthe demodulator 172 of a modulation pattern anticipated fortransmissions from the UE(s) 102.

The eNB operations module 182 may provide information 186 to the decoder166. For example, the eNB operations module 182 may inform the decoder166 of an anticipated encoding for transmissions from the UE(s) 102.

The eNB operations module 182 may provide information 101 to the encoder109. The information 101 may include data to be encoded and/orinstructions for encoding. For example, the eNB operations module 182may instruct the encoder 109 to encode transmission data 105 and/orother information 101. The other information 101 may include the DRBsand the RRC messages.

The encoder 109 may encode transmission data 105 and/or otherinformation 101 provided by the eNB operations module 182. For example,encoding the data 105 and/or other information 101 may involve errordetection and/or correction coding, mapping data to space, time and/orfrequency resources for transmission, multiplexing, etc. The encoder 109may provide encoded data 111 to the modulator 113. The transmission data105 may include network data to be relayed to the UE 102.

The eNB operations module 182 may provide information 103 to themodulator 113. This information 103 may include instructions for themodulator 113. For example, the eNB operations module 182 may inform themodulator 113 of a modulation type (e.g., constellation mapping) to beused for transmissions to the UE(s) 102. The modulator 113 may modulatethe encoded data 111 to provide one or more modulated signals 115 to theone or more transmitters 117.

The eNB operations module 182 may provide information 192 to the one ormore transmitters 117. This information 192 may include instructions forthe one or more transmitters 117. For example, the eNB operations module182 may instruct the one or more transmitters 117 when to (or when notto) transmit a signal to the UE(s) 102. The one or more transmitters 117may upconvert and transmit the modulated signal(s) 115 to one or moreUEs 102.

It should be noted that one or more of the elements or parts thereofincluded in the eNB(s) 160 and UE(s) 102 may be implemented in hardware.For example, one or more of these elements or parts thereof may beimplemented as a chip, circuitry or hardware components, etc. It shouldalso be noted that one or more of the functions or methods describedherein may be implemented in and/or performed using hardware. Forexample, one or more of the methods described herein may be implementedin and/or realized using a chipset, an application-specific integratedcircuit (ASIC), a large-scale integrated circuit (LSI) or integratedcircuit, etc.

FIG. 2 is a flow diagram illustrating one implementation of a method 200for establishing multiple connections by a UE 102. The UE 102 mayestablish 202 a first radio interface between the UE 102 and a firstpoint (e.g., first eNB 160) on an E-UTRAN. For example, the first eNB160 may belong to an E-UTRAN. In one configuration, the first eNB 160may be referred to as a primary eNB (PeNB). The UE 102 may connect 202to the first eNB 160 with a Uu interface. The Uu interface may also bereferred to as a primary Uu interface. The Uu interface may be a radiointerface between the UE 102 and the first eNB 160.

The UE 102 may establish 204 a second radio interface between the UE 102and a second point (e.g., second eNB 160) on the E-UTRAN by using thefirst radio interface. In one configuration, the UE 102 may beconfigured by the first eNB 160 to connect to the E-UTRAN with multipleradio interfaces. Therefore, upon connecting with the first eNB 160, theeNB 160 may configure the UE 102 to establish additional radiointerfaces using the first radio interface. The UE 102 may connect tothe second eNB 160 using the second radio interface. The second eNB 160may be referred to as a secondary eNB (SeNB). In one configuration, thefirst eNB 160 and the second eNB 160 have different schedulers. The UE102 may connect to the second eNB 160 with a Uux interface. The Uuxinterface may also be referred to as a secondary Uu interface.

The UE 102 may map 206 DRBs to at least one of the first radio interfaceand the second radio interface. In one configuration, all DRBs may bemapped 206 to one radio interface. For example, the user plane may useonly the Uux interface. Therefore, all DRBs may be mapped 206 to the Uuxinterface. Alternatively, all DRBs may be mapped 206 to the Uuinterface.

In another configuration, the DRBs may be organized into DRB sets thatmay be mapped 206 to different radio interfaces. For example, a firstDRB set may be mapped 206 to the first radio interface (e.g., the Uuinterface) and a second DRB may be mapped 206 to the second radiointerface (e.g., the Uux interface).

In some configurations, the UE 102 may also send one or more RRCmessages. The RRC protocol may convey control plane signaling, throughwhich the E-UTRAN may control the behavior of the UE 102. Formulti-connectivity operation (e.g., multiple Uu interface operation),the UE 102 may have one RRC connection, may have multiple RRCconnections or may have one RRC connection and multiple sub-RRCconnections. In one configuration, the one or more RRC messages sent bythe UE 102 may terminate at a single point on the E-UTRAN. For example,the UE 102 may send RRC messages toward a single point on the E-UTRAN.Therefore, the one or more RRC messages may terminate at one of thefirst eNB 160 or the second eNB 160.

In other configurations, the one or more RRC messages may terminate atmultiple points on the E-UTRAN. For example, the UE 102 may send RRCmessages toward multiple addressed points on the E-UTRAN. Therefore, atleast one RRC message may terminate at the first eNB 160 and at leastone RRC message may terminate at the second eNB 160.

FIG. 3 is a flow diagram illustrating one implementation of a method 300for establishing multiple connections by a first eNB 160. The first eNB160 may be similar to the eNB 160 described above in connection withFIG. 1. The first eNB 160 may connect 302 to a UE 102 with a first radiointerface. For example, the first eNB 160 may belong to an E-UTRAN. Inone configuration, the first eNB 160 may be referred to as a primary eNB(PeNB). The first eNB 160 may connect 302 to the UE 102 with a Uuinterface as described above in connection with FIG. 1. The first eNB160 may determine whether the UE 102 may be configured to connect to asecond eNB 160 with a second radio interface. In one configuration, thefirst eNB 160 may configure the UE 102 to connect to the E-UTRAN withmultiple radio interfaces. Therefore, upon connecting 302 with the UE102 (using the first radio interface), the first eNB 160 may configurethe UE 102 to establish additional radio interfaces.

The first eNB 160 may connect 304 to a second eNB 160. For example, uponbeing configured for multi-connectivity (using the first radiointerface), the UE 102 may connect to the second eNB 160 with a secondradio interface (e.g., Uux interface). The second eNB 160 may bereferred to as a secondary eNB (SeNB). The first eNB 160 may connect 304to the second eNB 160 to facilitate multi-connectivity and carrieraggregation. The first eNB 160 may connect 304 to the second eNB 160using one or more X interfaces. The first eNB 160 and the second eNB 160may exchange data (e.g., DRBs and RRC messages) across the one or more Xinterfaces. In one configuration, the first eNB 160 and the second eNB160 have different schedulers.

The first eNB 160 may map 306 DRBs to at least one of the first radiointerface and the second radio interface. In one configuration, all DRBsmay be mapped 306 to one radio interface. For example, the user planemay use only the Uux interface. Therefore, all DRBs may be mapped 306 tothe Uux interface. Alternatively, all DRBs may be mapped 306 to the Uuinterface.

In another configuration, the DRBs may be organized into DRB sets thatmay be mapped 306 to different radio interfaces. For example, a firstDRB set may be mapped 306 to the first radio interface (e.g., the Uuinterface) and a second DRB set may be mapped 306 to the second radiointerface (e.g., the Uux interface).

In some configurations, the first eNB 160 may also receive one or moreRRC messages. The RRC protocol may convey control plane signaling,through which the E-UTRAN may control the behavior of the UE 102. Formulti-connectivity operation (e.g., multiple Uu interface operation),the UE 102 may have one RRC connection, may have multiple RRCconnections or may have one RRC connection and multiple sub-RRCconnections. In one configuration, the one or more RRC messages receivedby the first eNB 160 may terminate at a single point on the E-UTRAN. Forexample, the first eNB 160 may receive all RRC messages sent by the UE102. Therefore, each of the one or more RRC messages may terminate atthe first eNB 160.

In other configurations, the one or more RRC messages may terminate atmultiple points on the E-UTRAN. For example, the UE 102 may send RRCmessages toward multiple addressed points on the E-UTRAN. The first eNB160 may determine whether an RRC message terminates at the first eNB 160or at the second eNB 160 based on an address included with an RRCmessage. Therefore, at least one RRC message may terminate at the firsteNB 160 and at least one RRC message may terminate at the second eNB160.

FIG. 4 is a block diagram illustrating configurations of E-UTRANarchitecture 423, 439 in which systems and methods for establishingmultiple connections may be implemented. The UE 402 a and UE 402 bdescribed in connection with FIG. 4 may be implemented in accordancewith the UE 102 described in connection with FIG. 1. In someconfigurations, both UEs 402 a-b may be implemented in a single device.The eNBs 460 a-c described in connection with FIG. 4 may be implementedin accordance with the eNB 160 described in connection with FIG. 1. TheeNBs 460 a-c may be a single device or multiple devices. In thetraditional E-UTRAN architecture 423, the E-UTRAN 435 a includes one ormore eNBs 460 a, providing the E-UTRA user plane (PDCP/RLC/MAC/PHY) andcontrol plane (RRC) protocol terminations towards the UE 402 a. The eNBs460 a may be interconnected with each other by an X2 interface (notshown in the figure). The eNBs 460 a may also be connected by the S1interface 431, 433 to the evolved packet core (EPC) 425 a. For instance,the eNBs 460 a may be connected to a mobility management entity (MME)427 a by the S1-MME 431 a interface and to the serving gateway (S-GW)429 a by the S1-U interface 433 a. The S1 interface 431, 433 supports amany-to-many relation between MMEs 427, serving gateways 429 and theeNBs 460 a. The S1-MME interface 431 a is the S1 interface 431, 433 forthe control plane and the S1-U interface 433 a is the S1 interface 431,433 for the user plane. The Uu interface 437 a is a radio interfacebetween the UE 402 a and the eNB 460 a for the radio protocol of E-UTRAN435 a.

The eNBs 460 a may host a variety of functions. For example, the eNBs460 may host functions for radio resource management (e.g., radio bearercontrol, radio admission control, connection mobility control, dynamicallocation of resources to UEs 402 a in both uplink and downlink(scheduling)). The eNBs 460 a may also perform IP header compression andencryption of user data stream; selection of an MME 427 a at UE 402 aattachment when no routing to an MME 427 a can be determined from theinformation provided by the UE 402 a; and routing of user plane datatowards the serving gateway 429 a. The eNBs 460 a may additionallyperform scheduling and transmission of paging messages (originated fromthe MME 427 a); scheduling and transmission of broadcast information(originated from the MME or operation and maintenance (O&M));measurement and measurement reporting configuration for mobility andscheduling; and scheduling and transmission of the public warning system(PWS) (which may include the earthquake and tsunami warning system(ETWS) and commercial mobile alert system (CMAS)) messages (originatedfrom the MME 427 a). The eNBs 460 a may further perform closedsubscriber group (CSG) handling and transport level packet marking inthe uplink.

The MME 427 a may host a variety of functions. For example, the MME 427a may perform Non-Access Stratum (NAS) signaling; NAS signalingsecurity; access stratum (AS) security control; inter core network (CN)node signaling for mobility between 3GPP access networks; and idle modeUE Reachability (including control and execution of pagingretransmission). The MME 427 a may also perform tracking area listmanagement (for a UE 402 a in idle and active mode); packet data networkgateway (PDN GW) and S-GW selection; MME 427 selection for handoverswith MME 427 change; and Serving GPRS Support Node (SGSN) selection forhandovers to 2G or 3G 3GPP access networks. The MME 427 a mayadditionally host roaming, authentication, and bearer managementfunctions (including dedicated bearer establishment). The MME 427 a mayprovide support for PWS (which includes ETWS and CMAS) messagetransmission, and may optionally perform paging optimization.

The S-GW 429 a may also host the following functions. The S-GW 429 a mayhost the local mobility anchor point for inter-eNB 460 a handover. TheS-GW 429 a may perform mobility anchoring for inter-3GPP mobility;E-UTRAN idle mode downlink packet buffering and initiation of networktriggered service request procedure; lawful interception; and packetrouting and forwarding. The S-GW 429 a may also perform transport levelpacket marking in the uplink and the downlink; accounting on user andQoS Class Identifier (QCI) granularity for inter-operator charging; andUL and DL charging per UE 402 a, packet data network (PDN), and QCI.

The radio protocol architecture of E-UTRAN 435 a may include the userplane and the control plane. The user plane protocol stack may includePDCP, RLC, MAC and PHY sublayers. The PDCP, RLC, MAC and PHY sublayers(terminated at the eNB 460 a on the network) may perform functions(e.g., header compression, ciphering, scheduling, ARQ and HARQ) for theuser plane. PDCP entities are located in the PDCP sublayer. RLC entitiesare located in the RLC sublayer. MAC entities are located in the MACsublayer. The PHY entities are located in the PHY sublayer.

The control plane may include a control plane protocol stack. The PDCPsublayer (terminated in eNB 460 a on the network side) may performfunctions (e.g., ciphering and integrity protection) for the controlplane. The RLC and MAC sublayers (terminated in eNB on the network side)may perform the same functions as for the user plane. The RRC(terminated in eNB 460 a on the network side) may perform the followingfunctions. The RRC may perform broadcast functions, paging, RRCconnection management, radio bearer (RB) control, mobility functions, UE402 a measurement reporting and control. The NAS control protocol(terminated in MME 427 a on the network side) may perform, among otherthings, evolved packet system (EPS) bearer management, authentication,evolved packet system connection management (ECM)-IDLE mobilityhandling, paging origination in ECM-IDLE and security control.

Signaling Radio Bearers (SRBs) are Radio Bearers (RB) that may be usedonly for the transmission of RRC and NAS messages. Three SRBs aredefined. SRB0 may be used for RRC messages using the common controlchannel (CCCH) logical channel. SRB1 may be used for RRC messages (whichmay include a piggybacked NAS message) as well as for NAS messages priorto the establishment of SRB2, all using the dedicated control channel(DCCH) logical channel. SRB2 may be used for RRC messages which includelogged measurement information as well as for NAS messages, all usingthe DCCH logical channel. SRB2 has a lower-priority than SRB1 and may beconfigured by E-UTRAN 435 a after security activation.

RRC connection establishment may involve the establishment of SRB1. Uponinitiating the initial security activation procedure, E-UTRAN 435 a mayinitiate the establishment of SRB2 and DRBs. The E-UTRAN 435 a may dothis prior to receiving the confirmation of the initial securityactivation from the UE 402 a.

PDCP may be established for each SRB1, SRB2, and DRB. RLC may beestablished for each SRB0, SRB1, SRB2, and DRB.

RRC may be responsible for the establishment, maintenance and release ofan RRC connection between the UE 402 a and the E-UTRAN 435 a includingallocation of temporary identifiers between the UE 402 a and the E-UTRAN435 a and configuration of SRBs for RRC connection, etc. RRC may beresponsible for the establishment, configuration, maintenance andrelease of point to point RBs.

The E-UTRAN architecture for multi-connectivity 439 is one example ofE-UTRAN architecture that may provide multi-connectivity for a UE 402 b.In this configuration, the UE 402 b may connect to E-UTRAN 435 b via aUu interface 437 b and a Uux interface 443. The E-UTRAN 435 b mayinclude a first eNB 460 b and a second eNB 460 c. The eNBs 460 b-c mayprovide the E-UTRA user plane (PDCP/RLC/MAC/PHY) and control plane (RRC)protocol terminations towards the UE 402 b. The eNBs 460 b-c may beinterconnected with each other by an X2 interface 493. The S1 interface431, 433 may support a many-to-many relation between MMEs 427 b, servinggateways 429 b and eNBs 460 b-c. The first eNB (e.g., PeNB) 460 b andthe second eNB (e.g., SeNB) 460 c may also be interconnected with eachother by means of one or more X interfaces 441, which may or may not bethe same as the S1-MME 431 b and/or X2 interface.

The first eNB 460 b and the second eNB 460 c may be connected by the S1interface 431, 433 to the EPC 425 b. The first eNB 460 b may beconnected to the MME 427 b by the S1-MME interface 431 b. The second eNB460 c may be connected to the serving gateway 429 b by the S1-Uinterface 433 b. The first eNB 460 b may behave as the MME 427 b for thesecond eNB 460 c so that S1-MME interface 431 b for the second eNB 460 cmay be connected (via the X interface 441, for instance) between thefirst eNB 460 b and the second eNB 460 c. Therefore, the first eNB 460 bmay appear to the second eNB 460 c as an MME 427 b (based on the S1-MMEinterface 431 b) and an eNB 460 (based on the X2 interface 493).

With this architecture 439, terminations on the E-UTRAN 435 b for the S1interface 431, 433 for user plane and for the control plane may beseparated. For example, the user plane may use the first eNB 460 b andthe S1-U interface 433 b and the control plane may use second eNB 460 cand the S1-MME interface 431 b. By separating S1 interface 431, 433between the user plane and the control plane, an MME 427 change may bemitigated as long as the UE 402 b is in the coverage of the first eNB460 b. Also, if a proxy gateway is located in between the second eNB 460c and S-GW 429 b, the mobility signal in the case of a handover betweenthe SeNBs would be mitigated. The proxy gateway may allow the S1interface 431, 433 between the SeNB and the EPC 425 b to support a largenumber of SeNBs in a scalable manner.

With the architecture 439 illustrated in FIG. 4, the first eNB 460 b(e.g., first point) may be connected to the mobility management entity(MME) and the second eNB 460 c (e.g., second point) may be connected toone or more of an S-GW 429 b and a proxy gateway between the second eNB460 c and the S-GW 429 b. The first eNB 460 b may be a termination forthe user plane protocol and the second eNB 460 c may be a terminationfor the control plane protocol.

It should be noted that both UEs 402 a-b described in connection withFIG. 4 may be implemented in the same device in some configurations. Forexample, a single device may include both the UE 402 a and the UE 402 b.Additionally or alternatively, one or more of the eNBs 460 a-c may be asingle device or multiple devices in some configurations.

FIG. 5 is a block diagram illustrating another configuration of E-UTRANarchitecture for multi-connectivity 539 in which systems and methods forestablishing multiple connections may be implemented. The UE 502described in connection with FIG. 5 may be implemented in accordancewith the UE 102 described in connection with FIG. 1. The eNBs 560 a-bdescribed in connection with FIG. 5 may be implemented in accordancewith the eNB 160 described in connection with FIG. 1. In thisconfiguration, the UE 502 may connect to E-UTRAN 535 via a Uu interface537 and a Uux interface 543. The E-UTRAN 535 may include a first eNB 560a and a second eNB 560 b. The eNBs 560 a-b may provide the E-UTRA userplane (PDCP/RLC/MAC/PHY) and control plane (RRC) protocol terminationstowards the UE 502. The eNBs 560 a-b may be interconnected with eachother by the X2 interface 593. The S1 interface 531, 533 may support amany-to-many relation between the MMEs 527, serving gateways 529 and theeNBs 560 a-b. The first eNB (e.g., PeNB) 560 a and the second eNB (e.g.,SeNB) 560 b may also be interconnected with each other by one or more Xinterfaces 541, which may or may not be the same as the S1-MME interface531, X2 interface 593, and/or the S1-U interface 533.

The first eNB 560 a may be connected by the S1 interface 531, 533 to theEPC 525. The first eNB 560 a may be connected to the MME 527 by theS1-MME interface 531 and to the serving gateway 529 by the S1-Uinterface 533. Therefore, the second eNB 560 b may not be connected tothe EPC 525. The first eNB 560 a may appear to the second eNB 560 b asan MME 527 (based on the S1-MME interface 531), an eNB (based on the X2interface 593), and an S-GW (based on the S1-U interface 533). Thisarchitecture 539 may provide a single node S1 interface 531, 533 (e.g.,connection) with the EPC 525 for the first eNB 560 a and the second eNB560 b. By the single node connection with EPC 525, MME 527 and S-GW 529,a change (e.g., handover) could be mitigated as long as the UE 502 is inthe coverage of the first eNB 560 a.

With the architecture 539 illustrated in FIG. 5, the first eNB 560 a(e.g., first point) may be connected to the MME 527 and to the servinggateway 529. The first eNB 560 a may be a termination for the user planeprotocol and a termination for the control plane protocol.

FIG. 6 is a block diagram illustrating a carrier aggregationconfiguration in which a first cell 645 and a second cell 647 areco-located, overlaid and have equal coverage. In traditional CA, two ormore component carriers (CCs) may be aggregated to support widertransmission bandwidths. A UE 102 may simultaneously receive or transmiton one or multiple CCs depending on the capabilities of the UE 102. Forexample, according to Rel-10 and later, a UE 102 with reception and/ortransmission capabilities for CA may simultaneously receive and/ortransmit on multiple CCs corresponding to multiple serving cells.According to Rel-8 and Rel-9, a UE 102 may receive on a single CC andtransmit on a single CC corresponding to one serving cell only.

When CA is configured, the UE 102 may have one radio resource control(RRC) connection with the network. One radio interface may providecarrier aggregation. During RRC connection establishment,re-establishment and handover, one serving cell may provide non-accessstratum (NAS) mobility information (e.g. tracking area identity (TAI)).During RRC connection re-establishment and handover, one serving cellmay provide a security input. This cell is referred to as the primarycell (PCell). In the downlink, the component carrier corresponding tothe PCell is the downlink primary component carrier (DL PCC) while inthe uplink it is the uplink primary component carrier (UL PCC).

Depending on UE 102 capabilities, secondary cells (SCells) may beconfigured to form together with the PCell a set of serving cells. Inthe downlink, the component carrier corresponding to an SCell is adownlink secondary component carrier (DL SCC) while in the uplink it isan uplink secondary component carrier (UL SCC).

The configured set of serving cells for a UE 102, therefore, may consistof one PCell and one or more SCells. For each SCell, the usage of uplinkresources by the UE 102 (in addition to the downlink resources) may beconfigurable. The number of DL SCCs configured may be larger than orequal to the number of UL SCCs and no SCell may be configured for usageof uplink resources only.

Additionally, according to the systems and methods disclosed herein, afirst radio interface may have a PCell and optionally one or more SCellsand a second radio interface may have a PCell and optionally one or moreSCells. However, in some configurations, the PCell of the second radiointerface may provide different functionalities than the PCell of thefirst radio interface. In some configurations, the PCell of the secondradio interface may provide a part of functionalities of the PCell ofthe first radio interface. In some configurations, the second radiointerface may not provide a PCell and may only provide one or moreSCells.

From a UE 102 viewpoint, each uplink resource may belong to one servingcell. The number of serving cells that may be configured depends on theaggregation capability of the UE 102. The PCell may only be changed withhandover procedure (e.g., with a security key change and random accesschannel (RACH) procedure). The PCell may be used for transmission of thephysical uplink control channel (PUCCH). Unlike the SCells, the PCellmay not be de-activated. Re-establishment may be triggered when thePCell experiences radio link failure (RLF), not when the SCellsexperience RLF. Furthermore, NAS information may be taken from PCell.

The reconfiguration, addition and removal of SCells may be performed byRRC. At intra-LTE handover, RRC may also add, remove or reconfigureSCells for usage with a target PCell. When adding a new SCell, dedicatedRRC signaling may be used for sending all required system information ofthe SCell (e.g., while in connected mode, UEs 102 need not acquirebroadcasted system information directly from the SCells).

As illustrated in FIG. 6, one CA deployment configuration includesfrequency 1 (F1) cells 645 and frequency 2 (F2) cells 647 that areco-located and overlaid. It should be noted that CA scenarios (e.g.,deployment configurations) may be independent of small cell scenarios.The eNBs 660 a-c described in connection with FIG. 6 may be implementedin accordance with the eNB 160 described in connection with FIG. 1. Inthis configuration, multiple eNBs 660 a-c may provide coverage for theF1 cells 645 and F2 cells 647. The systems and methods disclosed hereinmay be used to establish radio interfaces between the F1 cells 645 andF2 cells 647.

The coverage of the F1 cells 645 and the F2 cells 647 may be the same ornearly the same. Both layers (i.e., frequency layers) may providesufficient coverage and mobility can be supported on both layers. Alikely scenario for this configuration is when F1 and F2 are of the sameband (e.g., 2 GHz, 800 MHz, etc.). It is expected that CA is possiblebetween the overlaid F1 cell 645 and F2 cell 647.

FIG. 7 is a block diagram illustrating a carrier aggregationconfiguration in which F1 cells 745 and a F2 cells 747 are co-locatedand overlaid, but the F2 cells 747 have smaller coverage. The eNBs 760a-c described in connection with FIG. 7 may be implemented in accordancewith the eNB 160 described in connection with FIG. 1. In thisconfiguration, multiple eNBs 760 a-c may provide coverage for the F1cells 745 and the F2 cells 747. The systems and methods disclosed hereinmay be used to establish radio interfaces between the F1 cells 745 andF2 cells 747.

In this configuration, the F1 cells 745 and the F2 cells 747 areco-located and overlaid, but the F2 cells 747 have smaller coverage dueto larger path loss. Only the F1 provides sufficient coverage and the F2is used to improve throughput. Mobility is performed based on F1coverage. A likely scenario for this configuration is when the F1 andthe F2 are of different bands. For example, the F1 may equal 800 MHz or2 GHz and the F2 may equal 3.5 GHz, etc. It is expected that CA ispossible between the overlaid F1 cell 745 and F2 cell 747.

FIG. 8 is a block diagram illustrating a carrier aggregationconfiguration in which a F1 cells 845 and a F2 cells 847 are co-locatedbut the F2 antennas are directed to the cell boundaries of the F1. TheeNB 860 a-c described in connection with FIG. 8 may be implemented inaccordance with the eNB 160 described in connection with FIG. 1. Thesystems and methods disclosed herein may be used to establish radiointerfaces between the F1 cells 845 and F2 cells 847.

In this configuration, the F1 cells 845 and the F2 cells 847 areco-located but the F2 antennas are directed to the cell boundaries ofthe F1 so that cell edge throughput is increased. The F1 providessufficient coverage but the F2 potentially has holes (e.g., due tolarger path loss). Mobility is based on F1 coverage. A likely scenariofor this configuration is when the F1 and the F2 are of different bands.For example, the F1 may equal 800 MHz or 2 GHz and the F2 may equal 3.5GHz, etc. It is expected that the F1 cell 845 and the F2 cell 847 of thesame eNB 860 may be aggregated where coverage overlaps.

FIG. 9 is a block diagram illustrating a carrier aggregationconfiguration in which F1 provides macro coverage and remote radio heads(RRH) 949 a-j on F2 are used to improve throughput at hotspots. The eNB960 a-c described in connection with FIG. 9 may be implemented inaccordance with the eNB 160 described in connection with FIG. 1. In thisconfiguration, multiple eNBs 960 a-c may provide macro coverage for afirst cell 945. RRHs 949 a-j may be connected to the eNBs 960 a-c andmay provide second cell 947 coverage. The systems and methods disclosedherein may be used to establish radio interfaces between the F1 cells945 and F2 cells 947.

In this configuration, the F1 provides macro coverage and the remoteradio heads (RRH) 949 a-j on F2 are used to improve throughput athotspots. Mobility is performed based on F1 coverage. A likely scenariofor this configuration is when F1 and F2 are of different bands. Forexample, the F1 may equal 900 MHz or 2 GHz and F2 may equal 3.5 GHz,etc. It is expected that the F2 RRH cells 947 may be aggregated with theunderlying F1 cell 945 (e.g., the macro cells).

FIG. 10 is a block diagram illustrating a carrier aggregationconfiguration in which frequency selective repeaters 1051 a-c aredeployed. This configuration is similar to the configuration describedin connection with FIG. 7. The systems and methods disclosed herein maybe used to establish radio interfaces between the F1 cells 1045 and F2cells 1047. In this configuration, frequency selective repeaters 1051a-c are deployed so that coverage is extended for one of the carrierfrequencies. The eNBs 1060 a-c described in connection with FIG. 10 maybe implemented in accordance with the eNB 160 described in connectionwith FIG. 1. Multiple eNBs 1060 a-c may be associated with the F1 cells1045. It is expected that an F1 cell 1045 and an F2 cell 1047 may beaggregated where coverage overlaps.

FIG. 11 is a block diagram illustrating multiple coverage scenarios 1195for small cells with and without macro coverage. The eNBs 1160 a-kdescribed in connection with FIG. 11 may be implemented in accordancewith the eNB 160 described in connection with FIG. 1. The coveragescenarios 1195 include indoor and outdoor scenarios using low-powernodes (e.g., eNBs 1160 b-k). These low-power nodes may provide smallcell coverage (e.g., F2 coverage 1147). An eNB 1160 a may provide macrocell coverage (e.g., F1 coverage 1145)

Small cell enhancements may target both scenarios in which macrocoverage may or may not be present. The systems and methods describedherein may provide for establishing multiple connections in small celldeployment scenarios. These scenarios may include both outdoor andindoor small cell deployments and both ideal and non-ideal backhaul.Additionally, multiple connections may be established in both sparse anddense small cell deployments.

The E-UTRAN architecture may be able to achieve the system and mobilityperformance for small cell enhancement. For example, the systems andmethods described herein may provide the overall structure of controlplane and user plane and their relation to each other. For example, thecontrol plane and the user plane may be supported in different nodes,termination of different protocol layers, etc.

In a small cell deployment scenario, each node (e.g., eNB 1160 a-k) mayhave its own independent scheduler. To maximize the efficient use ofradio resources, a UE 102 may connect to multiple nodes that havedifferent schedulers. To connect to multiple nodes that have differentschedulers, multiple connections between the UE 102 and E-UTRAN 435 maybe established.

The first coverage scenario 1195 a illustrates a single small cell(e.g., the F2) with macro coverage (e.g., the F1). In FIG. 11, the F1 isthe carrier frequency for the macro layer, and the F2 is the carrierfrequency of the local-node layer. In the first coverage scenario 1195a, the macro cell may overlap the small cell.

The second coverage scenario 1195 b illustrates a single small cellwithout macro coverage. The third coverage scenario 1195 c illustratesmultiple small cells with overlapping macro cell coverage. The fourthcoverage scenario 1195 d illustrates multiple small cells without macrocell coverage.

FIG. 12 is a block diagram illustrating one configuration of a userplane protocol stack for multi-connectivity. The UE 1202 described inconnection with FIG. 12 may be implemented in accordance with the UE 102described in connection with FIG. 1. The eNBs 1260 a-b described inconnection with FIG. 12 may be implemented in accordance with the eNB160 described in connection with FIG. 1. A UE 1202 may connect to a PeNB1260 a and an SeNB 1260 b. The PeNB 1260 a may be similar to the firsteNB 160 and the SeNB 1260 b may be similar to the second eNB 160discussed in connection with FIG. 1.

In one configuration, the user plane protocol stack (e.g., PDCP2 1253,RLC2 1255, MAC2 1257 and PHY2 1259) may be mapped to a Uux interface443. For example, all DRBs may be mapped to one radio interface. In theconfiguration illustrated in FIG. 12, the user plane uses only the Uuxinterface 443. In other words, the user plane protocol stack (e.g.,PDCP2 1253 a, RLC2 1255 a, MAC2 1257 a and PHY2 1259 a) for the UE 1202terminates with the SeNB 1260 b and the user plane protocol stack (e.g.,PDCP2 1253 b, RLC2 1255 b, MAC2 1257 b and PHY2 1259 b) for the SeNB1260 b terminates with the UE 1202.

This configuration may achieve user plane and control plane separationbetween two radio interfaces (e.g., the Uu interface 437 and the Uuxinterface 443). Therefore, the control plane protocol stack may bemapped to a first radio interface (e.g., Uu interface 437) and the userplane protocol stack may be mapped to a second radio interface (e.g.,Uux interface 443). The Uu interface 437 does not provide DRBs and theUux interface 443 provides DRBs for the UE 102. This configuration maybe applied to both E-UTRAN architectures for multi-connectivity 439, 539of FIG. 4 and FIG. 5, but if the E-UTRAN architecture 439 of FIG. 4 isused, traffic on the X interface 441 may be significantly reduced.

FIG. 13 is a block diagram illustrating another configuration of a userplane protocol stack for multi-connectivity. The UE 1302 described inconnection with FIG. 13 may be implemented in accordance with the UE 102described in connection with FIG. 1. The PeNB 1360 a and SeNB 1360 bdescribed in connection with FIG. 13 may be implemented in accordancewith the eNB 160 described in connection with FIG. 1. A UE 1302 mayconnect to a PeNB 1360 a and a SeNB 1360 b. The PeNB 1360 a may besimilar to the first eNB 160 and the SeNB 1360 b may be similar to thesecond eNB 160 discussed in connection with FIG. 1.

In this configuration, a set of DRBs may be mapped to one radiointerface and another set of DRBs may be mapped to another radiointerface. The DRBs may be mapped to user plane protocol stacks (e.g.,PDCP, RLC, MAC and PHY). A first user plane protocol stack may be mappedto a first radio interface (e.g., Uu interface 437) and a second userplane protocol stack may be mapped to the second radio interface (e.g.,the Uux interface 443). For example, PDCP1 1361 and PDCP2 1353, RLC11363 and RLC2 1355, MAC1 1365 and MAC2 1357, PHY1 1367 and PHY2 1359 maybe the same sublayer but may have different entities. PDCP1 1361 a-b,RLC1 1363 a-b, MAC1 1365 a-b and PHY1 1367 a-b are mapped to the Uuinterface 437. PDCP2 1353 a-b, RLC2 1355 a-b, MAC2 1357 a-b and PHY21359 a-b are mapped to the Uux interface 443. In this configuration, theuser plane uses both the Uu interface 437 and the Uux interface 443.Therefore, both the Uu interface 437 and the Uux interface 443 provideDRBs.

In some configurations, the RRC may need to control sublayers for the Uuinterface 437 and the Uux interface 443 differently. The UE 1302 may beconfigured with DRBs to be mapped to either of radio interfaces 437,443. RRC messages which are sent from the E-UTRAN 435 to the UE 1302 maycarry information to configure and modify an identity of the Uuinterface 437 (e.g., the Uu interface 437 may be represented by anidentity of a Uu interface 437, an identity of a sub-RRC connection oran identity of an RRC connection) mapped to a radio bearer. DRBaddition, modification and release by RRC signaling may be associatedwith a certain radio interface (e.g., the Uu interface 437). DRBconfigurations (e.g., DRB addition, modification and release) mayinclude PDCP configuration, RLC configuration and/or logical channelconfiguration. SRB1 may be used to configure, modify and release DRBsfor the Uux interface 443.

FIG. 14 is a block diagram illustrating a configuration of a controlplane protocol stack for a single RRC connection. The UE 1402 describedin connection with FIG. 14 may be implemented in accordance with the UE102 described in connection with FIG. 1. The PeNB 1460 a and SeNB 1460 bdescribed in connection with FIG. 14 may be implemented in accordancewith the eNB 160 described in connection with FIG. 1. For multiple Uuinterface 437 operation, the UE 1402 may have one RRC connection, mayhave multiple RRC connections or may have one RRC connection andmultiple sub-RRC connections.

RRC messages may be exchanged between the UE 1402 and E-UTRAN 435 toestablish another RRC connection. RRC messages may also be exchangedbetween the UE 1402 and E-UTRAN 435 to establish one or more sub-RRCconnections. The Uu interface 437 may provide RRC signaling (e.g.,SRBs). The Uux interface 443 may or may not provide SRB0, SRB1 and/orSRB2. For example, the Uux interface 443 may transport only DRBs. SRB1may be used to configure, modify and release the DRBs for the Uuxinterface 443. In another example, the Uux interface 443 may provideSRB1 and SRB2. Both the Uu interface 437 and the Uux interface 443 mayshare the same SRBs. In yet another example, the Uux interface 443 mayprovide SRB1 and SRB2. The Uu interface 437 and the Uux interface 443may have their own SRBs. SRB1 on the Uu interface 437 may be used toconfigure, modify and release SRB1 for the Uux interface 443. This maybe applicable to the case of multiple RRC connections or multiplesub-RRC connections.

In FIG. 14, a UE 1402 may connect to a PeNB 1460 a and a SeNB 1460 b.The PeNB 1460 a may be similar to the first eNB 160 and the SeNB 1460 bmay be similar to the second eNB 160 discussed in connection withFIG. 1. An MME 1427 may provide a NAS message 1469 a-b (e.g.,piggybacked with the RRC messages 1471 a-b, for instance). The userplane protocol stack (e.g., PDCP1 1461 a-b, RLC1 1463 a-b, MAC1 1465 a-band PHY1 1467 a-b) is mapped to the Uu interface 437. In thisconfiguration, SRBs (e.g., RRC messages 1471 a-b) are provided over Uuinterface 437. In this case the Uux interface 443 provides only DRBs.

FIG. 15 is a block diagram illustrating a configuration of a controlplane protocol stack with multiple RRC connections. The UE 1502described in connection with FIG. 15 may be implemented in accordancewith the UE 102 described in connection with FIG. 1. The PeNB 1560 a andSeNB 1560 b described in connection with FIG. 15 may be implemented inaccordance with the eNB 160 described in connection with FIG. 1. In thisconfiguration, a UE 1502 may connect to a PeNB 1560 a and a SeNB 1560 b.The PeNB 1560 a may be similar to the first eNB 160 and the SeNB 1560 bmay be similar to the second eNB 160 discussed in connection withFIG. 1. An MME 1527 may provide a NAS message 1569 a-b (e.g.,piggybacked with the RRC messages 1571 a-b, for instance). A first userplane protocol stack (e.g., PDCP1 1561 a-b, RLC1 1563 a-b, MAC1 1565 a-band PHY1 1567 a-b) is mapped to the Uu interface 437. A second userplane protocol stack (e.g., PDCP2 1553 a-b, RLC2 1555 a-b, MAC2 1557 a-band PHY2 1559 a-b) is mapped to the Uux interface 443.

In this configuration, SRBs (e.g., RRC messages 1571 a-b) are providedover the Uu interface 437 and the Uux interface 443. The Uu interface437 and the Uux interface 443 may share the same SRBs. The X interface(and X protocol) 1541 a-b may be used to exchange data between SeNB 1560b and PeNB 1560 a. Although both radio interfaces are used to transportRRC messages 1571 a-b, the RRC protocol is terminated at one node. Forexample, the SeNB 1560 b transfers, to the PeNB 1560 a, RRC messages1571 a-b that are received from the UE 1502. Additionally, the SeNB 1560b transfers, to the UE 1502, RRC messages 1571 a-b that are receivedfrom the PeNB 1560 a. Therefore, RRC messages 1571 a-b may be terminatedat a single point on E-UTRAN 435. In other words, the UE 1502 may sendRRC messages toward a single point on E-UTRAN 435.

FIG. 16 is a block diagram illustrating one configuration of RRC message1671 management. The UE 1602 described in connection with FIG. 16 may beimplemented in accordance with the UE 102 described in connection withFIG. 1. The PeNB 1660 a and SeNB 1660 b described in connection withFIG. 16 may be implemented in accordance with the eNB 160 described inconnection with FIG. 1. In this configuration, a UE 1602 may connect toa PeNB 1660 a and a SeNB 1660 b. The PeNB 1660 a may be similar to thefirst eNB 160 and the SeNB 1660 b may be similar to the second eNB 160discussed in connection with FIG. 1. An MME 1627 may provide a NASmessage 1669 a-b (e.g., piggybacked with the RRC messages 1671 a-b, forinstance). A first user plane protocol stack (e.g., PDCP1 1661 a-b, RLC11663 a-b, MAC1 1665 a-b and PHY1 1667 a-b) is mapped to the Uu interface437. A second user plane protocol stack (e.g., PDCP2 1653 a-b, RLC2 1655a-b, MAC2 1657 a-b and PHY2 1659 a-b) is mapped to the Uux interface443.

In this configuration, illustrates one example of how to manage RRCmessages and parameters 1671 between the PeNB 1660 a and the SeNB 1660b. The RRC2 messages and parameters 1677 a-b for the Uux interface 443may be distinguished from the RRC1 messages and parameters 1675 for theUu interface 437. The X interface 1641 a-b may be used to exchange RRCmessages and parameters 1677 a-b for the SeNB 1660 b between the PeNB1660 a and the SeNB 1660 b. In this case, the RRC messages andparameters 1677 a-b for the SeNB 1660 b are called as RRC2.

FIG. 17 is a block diagram illustrating a configuration of a controlplane protocol stack with multiple control plane terminations. The UE1702 described in connection with FIG. 17 may be implemented inaccordance with the UE 102 described in connection with FIG. 1. The PeNB1760 a and SeNB 1760 b described in connection with FIG. 17 may beimplemented in accordance with the eNB 160 described in connection withFIG. 1. In this configuration, a UE 1702 may connect to a PeNB 1760 aand a SeNB 1760 b. The PeNB 1760 a may be similar to the first eNB 160and the SeNB 1760 b may be similar to the second eNB 160 discussed inconnection with FIG. 1. An MME 1727 may provide a NAS message 1769 a-b(e.g., piggybacked with the RRC messages 1771 a-b, for instance). Afirst user plane protocol stack (e.g., PDCP1 1761 a-b, RLC1 1763 a-b,MAC1 1765 a-b and PHY1 1767 a-b) is mapped to the Uu interface 437. Asecond user plane protocol stack (e.g., PDCP2 1753 a-b, RLC2 1755 a-b,MAC2 1757 a-b and PHY2 1759 a-b) is mapped to the Uux interface 443.

This configuration illustrates another example of a control planeprotocol stack with multiple control plane terminations. For instance,the RRC2 1777 a-b may be an additional RRC connection (e.g., in additionto RRC1 1775 a-b). RRC2 1777 a-b may be a sub-RRC connection in a singleRRC connection 1771 a-b. RRC messages 1775, 1777 may be terminated atmultiple points on the E-UTRAN 435. The UE 1702 may send RRC messages1775, 1777 which are addressed to one of multiple points (e.g., eNBs1760) on the E-UTRAN 435. The X interface 1741 a-b may be used toexchange RRC messages and parameters 1771 a-b between the PeNB 1660 aand the SeNB 1660 b.

The addressing of RRC messages 1775, 1777 may be achieved by identifyingan SRB to be used for conveying the RRC messages 1775, 1777. Theaddressing of RRC messages 1775, 1777 may also be achieved byidentifying a radio interface (e.g., Uu interface 437 and Uux interface443) to be used for conveying the RRC messages 1775, 1777. Theaddressing of RRC messages may further be achieved by identifying a typeof the RRC messages 1775, 1777. RRC parameters/messages 1777 for the Uuxinterface 443 may be distinguished from RRC parameters/messages 1775 forthe Uu interface 437. In a configuration where RRC2 1777 is anadditional RRC connection 1771, most of existing RRC functions andmessages are supported in both RRCs (e.g., RRC1 1775 and RRC2 1777). Butsome of functions and messages may not be supported in RRC2 1777. Inanother configuration where RRC2 1777 is sub-RRC connection 1771,limited functions and messages may be supported in RRC2 1777.

FIG. 18 illustrates various components that may be utilized in a UE1802. The UE 1802 described in connection with FIG. 18 may beimplemented in accordance with the UE 102 described in connection withFIG. 1. The UE 1802 includes a processor 1879 that controls operation ofthe UE 1802. The processor 1879 may also be referred to as a centralprocessing unit (CPU). Memory 1885, which may include read-only memory(ROM), random access memory (RAM), a combination of the two or any typeof device that may store information, provides instructions 1881 a anddata 1883 a to the processor 1879. A portion of the memory 1885 may alsoinclude non-volatile random access memory (NVRAM). Instructions 1881 band data 1883 b may also reside in the processor 1879. Instructions 1881b and/or data 1883 b loaded into the processor 1879 may also includeinstructions 1881 a and/or data 1883 a from memory 1885 that were loadedfor execution or processing by the processor 1879. The instructions 1881b may be executed by the processor 1879 to implement one or more of themethods 200 described above.

The UE 1802 may also include a housing that contains one or moretransmitters 1858 and one or more receivers 1820 to allow transmissionand reception of data. The transmitter(s) 1858 and receiver(s) 1820 maybe combined into one or more transceivers 1818. One or more antennas1822 a-n are attached to the housing and electrically coupled to thetransceiver 1818.

The various components of the UE 1802 are coupled together by a bussystem 1887, which may include a power bus, a control signal bus and astatus signal bus, in addition to a data bus. However, for the sake ofclarity, the various buses are illustrated in FIG. 18 as the bus system1887. The UE 1802 may also include a digital signal processor (DSP) 1889for use in processing signals. The UE 1802 may also include acommunications interface 1891 that provides user access to the functionsof the UE 1802. The UE 1802 illustrated in FIG. 18 is a functional blockdiagram rather than a listing of specific components.

FIG. 19 illustrates various components that may be utilized in an eNB1960. The eNB 1960 described in connection with FIG. 19 may beimplemented in accordance with the eNB 160 described in connection withFIG. 1. The eNB 1960 includes a processor 1979 that controls operationof the eNB 1960. The processor 1979 may also be referred to as a centralprocessing unit (CPU). Memory 1985, which may include read-only memory(ROM), random access memory (RAM), a combination of the two or any typeof device that may store information, provides instructions 1981 a anddata 1983 a to the processor 1979. A portion of the memory 1985 may alsoinclude non-volatile random access memory (NVRAM). Instructions 1981 band data 1983 b may also reside in the processor 1979. Instructions 1981b and/or data 1983 b loaded into the processor 1979 may also includeinstructions 1981 a and/or data 1983 a from memory 1985 that were loadedfor execution or processing by the processor 1979. The instructions 1981b may be executed by the processor 1979 to implement one or more of themethods 300 described above.

The eNB 1960 may also include a housing that contains one or moretransmitters 1917 and one or more receivers 1978 to allow transmissionand reception of data. The transmitter(s) 1917 and receiver(s) 1978 maybe combined into one or more transceivers 1976. One or more antennas1980 a-n are attached to the housing and electrically coupled to thetransceiver 1976.

The various components of the eNB 1960 are coupled together by a bussystem 1987, which may include a power bus, a control signal bus and astatus signal bus, in addition to a data bus. However, for the sake ofclarity, the various buses are illustrated in FIG. 19 as the bus system1987. The eNB 1960 may also include a digital signal processor (DSP)1989 for use in processing signals. The eNB 1960 may also include acommunications interface 1991 that provides user access to the functionsof the eNB 1960. The eNB 1960 illustrated in FIG. 19 is a functionalblock diagram rather than a listing of specific components.

FIG. 20 is a block diagram illustrating one configuration of a UE 2002in which systems and methods for sending feedback information may beimplemented. The UE 2002 includes transmit means 2058, receive means2020 and control means 2024. The transmit means 2058, receive means 2020and control means 2024 may be configured to perform one or more of thefunctions described in connection with FIG. 2 above. FIG. 18 aboveillustrates one example of a concrete apparatus structure of FIG. 20.Other various structures may be implemented to realize one or more ofthe functions of FIG. 2. For example, a DSP may be realized by software.

FIG. 21 is a block diagram illustrating one configuration of an eNB 2160in which systems and methods for receiving feedback information may beimplemented. The eNB 2160 includes transmit means 2117, receive means2178 and control means 2182. The transmit means 2117, receive means 2178and control means 2182 may be configured to perform one or more of thefunctions described in connection with FIG. 3 above. FIG. 19 aboveillustrates one example of a concrete apparatus structure of FIG. 21.Other various structures may be implemented to realize one or more ofthe functions of FIG. 3. For example, a DSP may be realized by software.

The term “computer-readable medium” refers to any available medium thatcan be accessed by a computer or a processor. The term“computer-readable medium,” as used herein, may denote a computer-and/or processor-readable medium that is non-transitory and tangible. Byway of example, and not limitation, a computer-readable orprocessor-readable medium may comprise RAM, ROM, EEPROM, CD-ROM or otheroptical disk storage, magnetic disk storage or other magnetic storagedevices, or any other medium that can be used to carry or store desiredprogram code in the form of instructions or data structures and that canbe accessed by a computer or processor. Disk and disc, as used herein,includes compact disc (CD), laser disc, optical disc, digital versatiledisc (DVD), floppy disk and Blu-ray® disc where disks usually reproducedata magnetically, while discs reproduce data optically with lasers.

It should be noted that one or more of the methods described herein maybe implemented in and/or performed using hardware. For example, one ormore of the methods described herein may be implemented in and/orrealized using a chipset, an application-specific integrated circuit(ASIC), a large-scale integrated circuit (LSI) or integrated circuit,etc.

Each of the methods disclosed herein comprises one or more steps oractions for achieving the described method. The method steps and/oractions may be interchanged with one another and/or combined into asingle step without departing from the scope of the claims. In otherwords, unless a specific order of steps or actions is required forproper operation of the method that is being described, the order and/oruse of specific steps and/or actions may be modified without departingfrom the scope of the claims.

It is to be understood that the claims are not limited to the preciseconfiguration and components illustrated above. Various modifications,changes and variations may be made in the arrangement, operation anddetails of the systems, methods and apparatus described herein withoutdeparting from the scope of the claims.

What is claimed is:
 1. A method by a User Equipment (UE) comprising:receiving, from a radio access network, one or more radio resourcecontrol (RRC) messages, wherein the one or more RRC messages are used:to configure a dual connectivity in which the UE communicates with theradio access network using a first set of cell(s) and a second set ofcell(s) and to configure a signaling radio bearer (SRB) for the secondset of cell(s), wherein the one or more RRC messages are sent via asignaling radio bearer of the first set of cell(s).
 2. A method by abase station comprising: transmitting, to a User Equipment (UE), one ormore radio resource control (RRC) messages, wherein the one or more RRCmessages are used: to configure a dual connectivity in which the UEcommunicates with a radio access network using a first set of cell(s)and a second set of cell(s) and to configure a signaling radio bearer(SRB) for the second set of cell(s), wherein the one or more RRCmessages are sent via a signaling radio bearer of the first set ofcell(s).
 3. A User Equipment (UE) comprising: a processor; and a memoryin electronic communication with the processor, wherein instructionsstored in the memory are executable to: receive, from a radio accessnetwork, one or more radio resource control (RRC) messages, wherein theone or more RRC messages are used: to configure a dual connectivity inwhich the UE communicates with the radio access network using a firstset of cell(s) and a second set of cell(s) and to configure a signalingradio bearer (SRB) for the second set of cell(s), wherein the one ormore RRC messages are sent via a signaling radio bearer of the first setof cell(s).
 4. A base station comprising: a processor; and a memory inelectronic communication with the processor, wherein instructions storedin the memory are executable to: transmit, to a User Equipment (UE), oneor more radio resource control (RRC) messages, wherein the one or moreRRC messages are used: to configure a dual connectivity in which the UEcommunicates with a radio access network using a first set of cell(s)and a second set of cell(s) and to configure a signaling radio bearer(SRB) for the second set of cell(s), wherein the one or more RRCmessages are sent via a signaling radio bearer of the first set ofcell(s).